Transition-Metal-Catalyzed 1,2-Carboboration of Alkenes: Strategies,Mechanisms, and Stereocontrol

During the past decade, many research groups have described catalytic methods for 1,2-carboboration, allowing access to structurally complex organoboronates from alkenes. Various transition metals, especially copper, palladium, and nickel, have been widely used in these reactions. This review summarizes advances in this field, with a special focus on the catalytic cycles involved in different metal-catalyzed carboboration reactions, as well as the regio- and stereochemical consequences of the underlying mechanisms. 1,2-Carboboration of other unsaturated systems, such as alkynes and allenes, is outside of the scope of this review.     

β-Selective C−H Arylation of Electron-Deficient Thiophenes,Pyrroles, and Furans

A general β-C−H arylation of electron-deficient thiophenes, pyrroles, and furans has been developed using ligand-modulated palladium catalyst. The use of a modified norbornene is crucial for reversing the conventional α-selectivity of these substrates. This method features good yields, high β-selectivity, and good tolerance of functional groups.     

Strengthen flame retardancy of epoxy thermoset by montmorillonite particles adhering phosphorus-containing fragments

Phosphaphenanthrene derivative tri-(3-DOPO-2-hydroxypropan-1-yl)-1,3,5-triazine-2,4,6-trione (TGD) and organo-modified montmorillonite (OMMT) were jointly introduced into the diglycidyl ether of bisphenol A cured by 4,4-diamino-diphenylmethane (EP) to investigate their flame retardant behaviors. With only addition of 0.5%OMMT and 2.5%TGD, epoxy thermoset achieved a limiting oxygen index value of 33.7% and passed UL 94 V-0 rating test. Compared with the combustion behaviors of 3%OMMT/EP and 3%TGD/EP, an obvious synergistic flame retardant effect between OMMT and TGD can be concluded in OMMT/TGD/EP. Meanwhile, the FTIR spectra of gas-phase and condensed-phase products further proved this synergistic effect working in a physical way. On one hand, the co-existence of hydroxyl-containing TGD enabled montmorillonite (MMT) particles to filtrate and adhere more smoke fragments. On the other hand, the co-action of MMT help the polar phosphorus-containing fragments from TGD better strengthened char layer, enhancing the barrier and protective effect of residue. The synergistic flame retardant effect from OMMT/TGD system endowed themselves with higher flame retardant efficiency, and epoxy thermoset with better flame retardant performance. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 47500.     

Action of silicic acid derived from sodium silicate precursor toward improving performances of porous gelatin membrane

To gain an insight into understanding how the silica network generated from hydrolysis and condensation of silicic acid, derived from sodium silicate, enhancing hydrothermal stability and mechanical properties of the leather, and particularly which active groups playing a main role for interaction of silica with collagen protein molecules, herein, effects of incorporated amino or carboxyl groups on the properties of silicic acid modified gelatin (GE) membrane were intensively studied. We found when lots of amino groups were introduced by adding a modified melamine, the thermal denaturation temperature, uniformity of pore diameter distribution and mechanical strength of GE membrane distinctly increased, while incorporating plenty of carboxyl groups by adding low polymerization degree acrylic acid polymer, no obvious change of performances of GE film was discovered. In addition, utilization of γ-glycidoxypropyltrimethoxysilane had a positive effect on the porosity and flexibility of GE membrane. Importantly, our results indicated that hydrogen bonding probably played the most important role toward improving performances of porous GE film when treated with silicic acid. These findings are greatly beneficial for developing a chrome-free tanning technology based on silicon containing materials, and are also suggestive for fabricating porous silica-GE hybrid materials using sodium silicate as a precursor. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48912.     

Antifouling performance enhancement of polyethersulfone ultrafiltration membrane through increasing charge-loading capacity over Prussian blue nanoparticles

Prussian blue (PB), as a kind of regulator of charge-loading capacity, was first used to modify polyethersulfone (PES) membrane, and a novel PB/PES ultrafiltration membrane was prepared by non-solvent induced phase separation method. The physicochemical properties of PB-NPs and PB/PES membranes were analyzed by Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscope, atomic force microscope, and zeta potential analysis. It was observed that PB-NPs were uniformly distributed in the PES matrix and a lotus-seedpod structure was formed inside the membrane. The addition of PB-NPs improved the charge-loading capacity of the PES membrane. The permeation and antifouling performance were investigated by filtering bovine serum albumin aqueous solution with different pH values. The results showed that the PB/PES membrane with 0.2-wt% PB-NPs content had the excellent antifouling performance and the flux recovery ratio value reached 90.73%. Moreover, the long-term stability test showed that PB-NPs did not fall off after continuous pure water filtration, indicating that PB/PES membrane had a good stability.     

A hybrid system of hydrogel/frog egg-like microspheres accelerates wound healing via sustained delivery of RCSPs

In this article, a hybrid system of hydrogel/frog egg-like microspheres (H-FMS) formed by the combination of coaxial electrostatic spraying and freeze-drying was introduced for enhancing wound healing efficiency through the sustained release of Rana chensinensis skin peptides (RCSPs). The porous PVA/gelatin hydrogel were obtained and frog egg-like microspheres (FMS) of sodium alginate (SA), shaping uniform and smooth, were embedded into hydrogel. Based on PVA/gelatin hydrogel, the FMS addition increased the water absorption of hydrogel to 1,105%. RCSPs were more effectively encapsulated into FMS than solid microspheres (MS). Not only does the H-FMS act as good “depots” for sustained release of RCSPs over 9 days, without exhibiting obvious burst release, but also show good biocompatibility in vitro. In vivo studies on wound healing as well as the histology of fibroblasts, re-epithelialization, inflammation, and hair follicles indicated that the structure of H-FMS released RCSPs continuously and promoted wound healing in rats significantly.     

低温蒸发联合臭氧催化氧化处理精细化工污水

某生产清洗剂类化工品的企业属典型小型精细化工企业,生产污水只能采用企业自理的处理方式,随着企业产品种类和数量的增多,产生的污水量及污水污染物已远超过原处理设施的处理能力。本研究采用低温蒸发联合臭氧催化氧化的短流程处理工艺,组装成移动式一体化处理设备处理该废水,处理结果表明,出水COD≤30 mg/L、总磷≤0.5 mg/L、浊度≤6.0 mg/L、色度接近0,达到国家一级排放标准和回用标准。     

石墨烯改性涂层防护性能研究

为减少团聚，提高石墨烯在涂层中的分散性，研究采用纳米分散技术预先制备了石墨烯分散液，再将其分散至环氧树脂中获得石墨烯改性复合涂层。通过对石墨烯含量为 0、0.3%、0.6%的复合涂层进行盐水浸泡、盐雾、阴极剥离实验及电化学性能测试，证明石墨烯的加入显著增强了涂层的防护性能。石墨烯复合涂层在 3.5%盐水中浸泡 1 008 h后，涂层低频阻抗仍大于 106 Ω·cm²比未添加石墨烯的涂层提高了 3个数量级，且盐雾实验 6 000 h后涂层表面仍保持完好；含 0.6%石墨烯，的涂层耐蚀行为劣于石墨烯含量为 0.3%的涂层。     

作业成本法在新田煤矿成本控制和管理中的应用研究

为了提升新田煤矿作业预算、过程控制、效果考核评价等精细化管理水平,降本增效的作业点以及综合成本,采用作业成本法对新田煤矿成本控制和管理进行了研究,建立了组织机构明确管控项目,研究作业成本核算体系以及作业成本法执行体系。研究得出,作业成本法能为企业产品定价、生产决策、市场定位以及成本控制决策等提供准确成本信息。